Hello Anja. Below is the classification info from the
American Iris Society site. One bud per stem is typical
for MDB class.

John B

1. Miniature Dwarf Bearded (MDB) -- the tiniest of bearded irises, with height of up to 20 cm (8 inches). They are also the earliest to bloom. They are most effective in rock gardens or planted in drifts where they make a "carpet of color."

2. Standard Dwarf Bearded (SDB) -- some of the most useful garden plants, ranging in height from 20 cm (8 inches) to 41 cm (16 inches). They begin their bloom as the MDBs are ending, still quite early in the iris season. They are best displayed in clumps where they give the effect of a "cushion" of individual blooms. The colors are nearly unlimited since the SDBs show all the different "spot patterns" of the miniatures, as well as the plicatas and pinks seen in the TBs.

--- In i*@yahoogroups.com, "Anja Pansin/Wolfgang Zirkel" <zirpan@...> wrote:
>
> This is another favorite seedling of mine (parentage unknown). But I am not sure if it is a SDB or a MDB. The flower is very very small. Unfortunately it has only one bud per stem.
> Anja Germany zone 6
>